﻿40 
  THE 
  BEAN 
  THRIPS. 
  

  

  In 
  the 
  section 
  around 
  Compton, 
  Cal., 
  the 
  adults 
  were 
  found 
  to 
  

   hibernate 
  in 
  small 
  numbers 
  on 
  the 
  underside 
  of 
  leaves 
  of 
  nasturtium, 
  

   sugar 
  beets, 
  wild 
  heliotrope, 
  and 
  other 
  plants. 
  They 
  were 
  also 
  found 
  

   hiberating 
  in 
  some 
  numbers 
  in 
  dead 
  leaves 
  and 
  rubbish. 
  When 
  dis- 
  

   turbed 
  they 
  were 
  sluggish 
  and 
  made 
  little 
  effort 
  to 
  escape. 
  

  

  Mr. 
  P. 
  E. 
  Jones 
  (in 
  litt.) 
  says 
  that 
  around 
  Lindsay, 
  Cal., 
  the 
  adults 
  

   hibernate 
  in 
  numbers 
  in 
  the 
  navel 
  end 
  of 
  the 
  Washington 
  navel 
  

   orange. 
  He 
  also 
  stated 
  that 
  in 
  midwinter 
  he 
  had 
  taken 
  this 
  thrips 
  

   along 
  creek 
  beds 
  hibernating 
  on 
  the 
  underside 
  of 
  leaves 
  of 
  wild 
  rasp- 
  

   berry 
  and 
  blackberry 
  which 
  were 
  istill 
  on 
  the 
  plants. 
  

  

  NOTES 
  ON 
  OCCURRENCE. 
  

  

  Apparently 
  the 
  different 
  methods 
  of 
  cultivation 
  bear 
  strongly 
  on 
  the 
  

   abundance 
  of 
  these 
  insects 
  and 
  consequent 
  injury 
  they 
  may 
  cause 
  to 
  a. 
  

   crop. 
  In 
  Los 
  Angeles 
  County, 
  where 
  clean 
  cultivation 
  is 
  not 
  strictly 
  

   followed 
  out, 
  it 
  begins 
  to 
  breed 
  in 
  the 
  spring 
  on 
  the 
  wild 
  food 
  plants 
  

   and 
  increases 
  more 
  and 
  more 
  until 
  in 
  August 
  it 
  has 
  reached 
  enormous 
  

   numbers. 
  Before 
  this 
  the 
  native 
  plants 
  are, 
  many 
  of 
  them, 
  either 
  

   matured 
  or 
  destroyed 
  by 
  the 
  thrips, 
  and 
  as 
  a 
  result 
  it 
  spreads 
  more 
  

   and 
  more 
  to 
  the 
  cultivated 
  crops 
  and 
  trees 
  that 
  serve 
  as 
  hosts. 
  Dur- 
  

   ing 
  some 
  years 
  this 
  occurs 
  late 
  in 
  the 
  season 
  and 
  very 
  little 
  real 
  

   damage 
  results, 
  but 
  if 
  this 
  insect 
  should 
  begin 
  the 
  year 
  in 
  fairly 
  large 
  

   numbers 
  and 
  under 
  favorable 
  conditions, 
  great 
  damage 
  may 
  result. 
  

  

  In 
  Ventura 
  County, 
  in 
  October, 
  1910, 
  the 
  author 
  made 
  a 
  careful 
  

   examination 
  of 
  the 
  entire 
  bean-growing 
  section 
  and 
  found 
  that 
  the 
  

   bean 
  thrips 
  occurred 
  in 
  extremely 
  small 
  numbers 
  on 
  the 
  little 
  vege- 
  

   tation 
  remaining. 
  At 
  the 
  same 
  time 
  it 
  was 
  extremely 
  abundant 
  

   around 
  Compton. 
  This 
  condition 
  seemed 
  to 
  be 
  a 
  direct 
  result 
  of 
  the 
  

   practice 
  of 
  the 
  growers 
  in 
  Ventura 
  of 
  thoroughly 
  plowing 
  and 
  culti- 
  

   vating 
  the 
  fields 
  within 
  a 
  short 
  time 
  after 
  the 
  beans 
  are 
  harvested 
  

   and 
  keeping 
  them 
  in 
  perfect 
  condition 
  until 
  the 
  next 
  crop 
  is 
  planted. 
  

   This 
  advantage 
  is 
  increased 
  because 
  there 
  is 
  very 
  little 
  waste 
  space 
  

   where 
  weeds 
  can 
  grow 
  up. 
  Our 
  investigations 
  during 
  the 
  past 
  two 
  

   years 
  have 
  shown 
  that 
  this 
  insect 
  is 
  not 
  abundant 
  on 
  cultivated 
  crops 
  

   in 
  the 
  spring 
  or 
  early 
  summer, 
  but 
  that 
  after 
  this 
  period 
  it 
  increases 
  

   more 
  and 
  more, 
  and 
  in 
  certain 
  years 
  injures 
  them 
  so 
  severely 
  as 
  to 
  

   cause 
  much 
  loss. 
  

  

  NATURAL 
  CONTROL. 
  

  

  RAINS. 
  

  

  One 
  of 
  the 
  largest 
  factors 
  in 
  the 
  destruction 
  of 
  thrips 
  in 
  some 
  

   localities 
  is 
  the 
  prevalence 
  of 
  hard, 
  dashing 
  rains. 
  The 
  author, 
  

   while 
  working 
  in 
  Florida 
  with 
  the 
  greenhouse 
  thrips, 
  once 
  observed 
  

  

  